1. Field of the Invention
This invention relates generally to a magnetic disk drive, and more particularly to an electrical connection technique for supplying a write signal to a magnetic head or recalling a signal, which has been read by the magnetic head, from the magnetic disk drive.
2. Description of the Related Art
Recently, the trend is to reduce the size and thickness of magnetic disk drives. Also, realization of magnetic disk drives/which consume only a small amount of electric power is required. Further, improvement of recording density of a magnetic disk is demanded in order to fulfill the requirement for the magnetic disk drive of having a larger capacity, and therefore, the number of magnetic disks to be loaded on the magnetic disk drive is increased.
A magnetic disk drive for computers generally employs a contact start and stop (CSS) system for regulating a relation between a head and a magnetic disk. According to this system, the head is raised slightly upwardly from the magnetic disk during the rotation of the magnetic disk, keeping only a very small space between the head and the magnetic disk. The head is raised because of a balance of force between a floating force produced by an air flow caused by high-speed rotation of the magnetic disk and a force of a spring arm. When the magnetic disk stops rotating, the head moves to a contact allowable area on the disk where the head contacts the disk. During the time the magnetic disk stops rotation, the head is kept in contact with the magnetic disk.
Heretofore, in order to supply write signals to a magnetic head or in order to recall signals, which have been read by the magnetic disk, outside from the magnetic disk drive, lead wires attached to a spring arm (suspension) are used. However, as the magnetic disk drive is gradually down-sized, the construction of the spring arm is changed from the type in which the spring arm has lead wires attached thereto, to the type in which the spring arm has a conductor pattern connected to the magnetic head and integral with the surface of the spring arm.
In the conventional disk drive in which the spring arm having a conductor pattern is employed, a main flexible printed circuit sheet (hereinafter referred to as the "main FPC") is disposed within the disk drive. The main flexible printed circuit sheet is employed to provide a wiring to an electronic circuit unit which is placed outside the magnetic disk drive. Terminals disposed at a basal end portion of the spring arm and terminals of the main FPC are connected to each other by way of lead wires. Since a distal end portion of the main FPC is secured to an actuator arm by adhesive or screw means, the lead wires are laid along the side surface of the actuator arm.
A magneto-resistive head (MR head) or compound head is recently developed as a head of a magnetic disk drive. This MR head is designed such that an inductive element is used when data is written and an magneto-resistive element (MR element) is used when data is read. Consequently, signal wires (or signal conductors) are increased in number from two, as had by the typical conventional head, to four. Therefore, if the terminals of the spring arm and the terminals of the main FPC are connected to each other by way of lead wires as in the prior art, the number of the steps for wiring and assembling are increased by double. Further, since the number of the terminals is increased, the space for installing the terminals of the spring arm and main FPC is also required twice as large as ever. However, since the recent magnetic disk drive is gradually made smaller and smaller and thinner and thinner, it becomes increasingly difficult to obtain a sufficient space for the terminals portion. As a consequence, the terminals portion becomes smaller and a space between adjacent terminals is unavoidably decreased.
Because of the reasons set forth herein before, it is not desirable to use lead wires for interconnecting the terminals of the spring arm and main FPC, but it is desirable to interconnect the terminals of the spring arm and main FPC by way of a relaying flexible printed circuit sheet (hereinafter referred to as the "relaying FPC"). In case the terminals are interconnected by the relaying PFC, a technique for simultaneously connecting a plurality of terminals by soldering, gold contact adhesion, or the like is required. Since there is a possibility of the need of some repairing such as replacement of the head due to mismatch of characteristics between the magnetic disk and the head when the magnetic disk drive is assembled, soldering is advantageous for interconnecting the terminals because repeated connection can be made by soldering.
However, since the terminals portion becomes smaller and the space between the terminals becomes narrower as the downsizing of the magnetic disk drive is further progressed, a required quantity of solder becomes smaller. Therefore, it can be easily imagined that the normal solder connecting technique is not enough to cope with the short-circuit troubles between the terminals and cannot provide a sufficient strength of connection between the terminals. Further, since old solder used before the repairing operation is partly remained on the terminal or terminals when the head is replaced/repaired, stability of the quality of connection becomes more difficult to obtain.